Pluto (Planet)

Updated : 05/04/2025

Pluto for years was known as the ninth planet and the furthest planet from the Sun. Clyde Tombaugh spotted Pluto as he scanned photos of the sky, looking for any differences in the pictures.

Reclassification

Since its discovery in the 1930s until 2005, Pluto was a planet, the most distant from the Sun. However, when astronomers discovered the kuiper belt object Eris in 2003, its days of being a planet were numbered. Eris with its companion moon Dysnomia was calculated to be larger than Pluto. Scientists did not want to call it a planet and devised a three-point law on what constitutes a planet. A vote was held at the end of the International Astronomical Union meeting, the world governing body for all things to do with space. A vote was held on the law and agreed. It has the asteroid ID of 134340. The requirements for a planet are:-

• is in orbit around the Sun
• has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a nearly round shape
• has cleared the neighbourhood around its orbit.

As Pluto failed the third test, it was demoted and no longer considered a planet. The third rule is flawed and could rule out Earth as a planet because some asteroids have been known to cross its path. There are plans afoot to reclassify it. The lead scientist on the New Horizons project was extremely scathing of the downgrading, saying it stunk but could have used harsher words. The planet is named after the Roman God of the Underworld. It is not named after the Disney dog of the same name. Venetia Burney, a British schoolgirl who entered a competition to name it, named it.

New Horizons Probe

Pluto was the last "planet" to be visited by a spacecraft, but that is all about to change. The N.A.S.A. space probe, New Horizons, is en route to rendezvous with the "planet" on or about 14th July 2015. New Horizons is the fastest spacecraft built to explore the outer regions of space. It took Cassini-Huygens just over three years to reach the orbit of Jupiter. The New Horizons craft took a third of that time.

New Horizons only flew past the planet because the probe had insufficient fuel to slow it down. It would have taken longer to get there if it had the necessary fuel to slow it down. Pluto is not the end of the journey for New Horizons; it is carrying on to rendezvous with an asteroid in the Kuiper Belt called 2014 MU69, which will arrive at the beginning of 2019. ref: N.A.S.A.

According to scientists looking at the data that has come back from the New Horizons probe, they believe they discovered water ice on the planet. Where there is water, there could be life, albeit at a fundamental microbial level. The New Horizons probe was not equipped with devices that could confirm any life forms on the planet. Life on such a cold and far-off planet would be something. N.A.S.A.

The picture below is the first clear photo of what Pluto looks like with its distinctive heart shape. It was taken when the New Horizons craft flew past the celestial body.

Disney's Pluto Dog

Before anyone gets the wrong idea, let us clear a thing up about it and a certain cartoon animal. Pluto is not named after a cartoon dog. Disney named its cartoon dog Pluto in honour of the discovery, not vice versa. Pluto was named after the Ancient Roman God Pluto, the God of the Underworld, as mentioned above. All the other planets except Earth are named after a Roman God, so it made sense to continue the ritual.

Pluto had for most of the time it was known was seen as a lonely planet like Mercury and Venus but on the 22nd June 1978, its first moon was discovered by James Christy at the United States Naval Observatory. After launching New Horizons, its other moons were discovered, starting with Nix in 2005. All The Moons are named after a connection to the underworld to keep consistent.

Life on Pluto

There is no intelligent life, no Plutonians living and breathing on the planet. One of the surprising things discovered by the New Horizons mission was evidence of water on the planet and that there might be an ocean on the planet. Any water would be frozen unless there is an underground heat source. Where there is water, there could be life in microbial life forms. Life exists in Earth's harshest atmospheres, so why not on Pluto? ref:Astrobio

Pluto is unlikely to have any complex life forms. However, as the Sun grows, it will get bigger, the Goldilocks Zone will move out, and one day, that zone will encompass Pluto. By the time the zone reaches Pluto, Earth will no longer be able to support life as we know it. Hopefully, by then, humanity has found a way off the planet and live further than Pluto.

Search

Scientists believe there might be another planet out beyond the orbit of Pluto, a new ninth planet. It is all theory at the moment, but one day, we may find out if there are any large planets beyond Pluto. There might well be more than just one planet beyond Pluto, maybe tens, all too faint to be spotted by telescopes.

One of the strongest drivers for another planet is in the paths of objects in the Kuiper Belt, which seemingly behave differently from how they are supposed to be. There is a theory that the reason is that the ninth planet was chucked out of at the beginning. As it is so far away, it is hard to see, and you definitely will not be able to see it looking up into the night sky.

Pluto Facts

• Pluto is the ex-nineth planet from the Sun. It is now classed as a dwarf planet, too big and too spherical to be classed as an asteroid but its path is not clear hence it fails the IAU requirement of a planet.
• There are so far 5 known moons (Confirmed) in orbit round Pluto.
• Pluto was discovered in 1930 by Clyde Tombaugh.
• The planet is classed as a dwarf planet.
• Pluto derives its name from the Roman god for God of Death.
• Pluto was discovered by Clyde Tombaugh in 1930.
• The Mass of the planet is 0.01303 (10^24) kg.
• The Equatorial Radius of the planet is 1,188.00km whereas the volumetric mean radius is 1,188.00 km.
• The Equatorial Circumference of the Pluto is 7,231.9km.
• The Mean Density of the planet is 1860 kg/m³.
• The Surface Acceleration of the planet is 0.62 m/s².
• The time the planet takes to orbit (Orbital Period) round the Sun is 90560 days or roughly 248.1 Earth Years.
• The length of a day on the planet is 153.282 hours, i.e. the time it takes to revolve once on its axis.
• The Average Temperature of the planet is -50K/-223C.
• The Surface Pressure of the planet is ~10 microbars .
• The Semi-Major Axis of the planet is 39.4816867700 A.U.
• Pluto Distance from the Sun is about 5,906,380,000.0km.
• The Orbit Eccentricity is 0.2488 degrees, that is how much the orbit deviates from a circle, between 0 and 1.
• The Orbit Inclination is 17.16 degrees, that is how much the orbit deviates from the orbital plane.
• The volume of Pluto at the equator is 0.967.
• The Escape Velocity, the speed which is need to break free is 2.21 kilometers per second.
• The Surface Gravity of Pluto is 0.62 compared to Earth which for purpose of this site is 1.
• The following gasses can be found in the Pluto's Atmosphere :
  • Methane (CH4).
  • Nitrogen (N2).
• More information and the source for the moon can be found at N.A.S.A.
• The page was last updated on 4/5/2025 4:54:00 pm.